1. Field of the Invention
The present invention relates to a spread illuminating apparatus, and more particularly to a spread illuminating apparatus used as an illuminating means for a liquid crystal display.
2. Description of the Related Art
A liquid crystal display (hereinafter referred to as xe2x80x9cLCDxe2x80x9d) featuring low profile and light weight as well as low power consumption has been extensively used in electric products including cellular phones and personal computers, and the demand for the LCD has been increasing. However, since a liquid crystal which is a structural element of the LCD does not emit light by itself unlike a light emitting element such as a CRT, the LCD requires a separate illuminating means for irradiating the LCD to obsess: an image. In particular, to satisfy a recent demand for downsizing, a sheet-like spread illuminating apparatus of side light type (light conductive plate type) is often used. As an example of a spread illuminating apparatus of side light type, an apparatus proposed by the present applicant was disclosed in Japanese Patent Application No. 2001-027122.
As shown in FIG. 5, a spread illuminating apparatus 1 generally comprises a light conductive plate 2 made of a light-transmissible material and a bar-like lamp 4 disposed along and close to a side surface 3 of the light conductive plate 2. In the spread illuminating apparatus 1 which is a front lighting system as an auxiliary lighting device, light emitted from the lamp 4 is guided into light conductive plate 2 and irradiates an LCD (not shown) disposed under the light conductive plate 2. The lamp 4 is generally composed of a light conductive bar 5 made of a transparent material and disposed along and close to the side surface 3 of the light conductive plate 2, spot-like light sources 6 and 7 arranged to face end surfaces 5a and 5b of the light conductive bar 5, respectively, and a light reflection member 23.
A light reflection pattern 8 is formed on one major surface (hereinafter referred to as xe2x80x9ctop surfacexe2x80x9d) of the light conductive plate 2. A light reflection pattern cover 9 is disposed over the top surface of the light conductive plate 2 with a connecting member (not shown) provided therebetween so as to cover the light reflection pattern 8. The connecting member is shaped like a rim corresponding to the periphery of the light conductive plate 2. A cushioning material (not shown) made of a gel or liquid transparent substance is inserted between the light conductive plate 2 and the light reflection pattern cover 9 and along the inside of the connecting member.
The spread illuminating apparatus 1 of FIG. 5 is provided with the light reflection pattern cover 9 thereby keeping dust out of the light reflection pattern 8 and also preventing damage to the surface of the light conductive plate 2.
The light conductive plate and the lamp of the spread illuminating apparatus 1 are integrally enclosed in a picture frame-like housing made of, for example, a resin material, to be set in a cellular phone or the like.
By providing the light reflection pattern cover 9 over the top surface of the light conductive plate 2, the light reflection pattern 8 can be completely dust-free as described above. However, because the light reflection pattern cover is desired to be small to a minimum in thickness to reduce the thickness of the spread illuminating apparatus as a whole, the surface of the light conductive plate may not always be sufficiently protected against an impact from tie outside. In addition, a good-quality cushioning material with a lower refractive index than that of the light conductive plate 2 is not easily available, inevitably pushing up cost.
A frame-like plate, which is a display side part of a casing of a display product such as a cellular phone, has a transparent cover (hereinafter referred to as xe2x80x9cviewing area coverxe2x80x9d) positioned over the spread illuminating apparatus 1, to be specific, over the light reflection pattern cover 9. This viewing area cover prevents dust from getting in the casing. It is a general practice to provide the viewing area cover in order to protect the spread illuminating apparatus mounted on the display product.
In the spread illuminating apparatus 1, however, when the frame-like plate of the display product is detached during or after mounting the apparatus 1 (the frame-like plate can be detached by the user in some products), the top surface of the spread illuminating apparatus 1 is exposed, so that dusts or foreign materials may get in a gap between the light conductive plate 2 and the housing 27, or may cause damage to the outside surface of the housing.
The present invention has been made in light of the above, and its object is to provide a spread illuminating apparatus which can prevent dusts or foreign materials from getting stuck to or damaging not only the surface of a light reflection pattern formed on a light conductive plate but also the surfaces of other components, and which is still less expensive and smaller in thickness than a conventional spread illuminating apparatus.
In a spread illuminating apparatus according to the present invention, which comprises a regular light conductive plate having a light reflection pattern on one major surface thereof, a bar-like lamp disposed at at least one side surface of the light conductive plate, and a housing adapted to hold together the light conductive plate and the lamp, which constitutes, together with a liquid crystal display, a display product, and which is disposed in front of a liquid crystal display panel, a cover made of a light-transmissible material and adapted to cover a top surface of the light conductive plate and a surface of the amp is fixed to the housing so as to concurrently serve as a viewing area cover conventionally supposed to be attached on a casing of the display product.
In the spread illuminating apparatus according to the present invention, the cover is made of an acrylic resin or a glass material.
In the spread illuminating apparatus according to the present invention, the cover is fixed to the housing with an adhesive double coated tape.